This invention relates generally to conveyor systems for use in manufacturing operations such as automated assembly systems or machine tool loading operations. Improved carriers are provided with a bumper having braking capabilities to reduce shock transmitted when one moving or oncoming carrier impacts into a stationary or slowly moving queued carrier in a conveyor system. The bumper of the present invention is mounted so that it can swivel as the carrier makes a turn in a conveyor system.
Automated conveyor systems for the assembly of products are well-known. An example of a track system in which the present invention has application is shown and described in U.S. Pat. No. 5,447,220. The present invention is directed to non-synchronous assembly systems and specifically to the problem encountered when a moving carrier impacts a stationary or queued carrier along a conveyor track. The present invention is directed to an improved system that buffers the collision between two carriers, thereby reducing shock transmitted to the products disposed on top of the carriers. The present invention includes a pivoting bumper which improves the ability of a carrier to make turns in a conveyor system without getting wedged in the event that an impact occurs when two carriers are not aligned.
Workpieces are transported by carriers from stage to stage in an assembly system which ride in a track on top of the conveyor or conveyor chain. In a synchronous assembly system, a workpiece and carrier proceed through each stage of the assembly process and do not proceed to the next stage until the remaining workpieces are also ready to proceed to the next stage (i.e., each workpiece is in synch with the other workpieces). Thus, in synchronous assembly systems, the conveyor stops after each workpiece arrives at its respective processing stage, and the stage or task that takes the greatest amount of time will limit the rate at which all other tasks or stages can be completed because the conveyor will not resume a forward motion until all the workpieces, including the workpiece at the slowest stage, are ready to proceed to the next stage.
In contrast, in non-synchronous assembly systems, the conveyor moves continuously forward. Slower tasks are performed in multiple by employing combinations of divide modules or divide sections. At a divide section, carriers are routed from the main conveyor to spurs so that the slow task may be performed on a number of workpieces on the conveyor system at the same time. Divide sections are designed to send workpieces with the slowest task completed down the conveyor at the line rate or the rate at which the main conveyor chain is moving. After a slower task is completed, the workpiece is returned to the main conveyor chain via a merge module. A slower assembly task may also be performed by physically removing the workpiece and carrier from the conveyor, performing the task, and returning the workpiece and carrier to the conveyor where the workpiece and carriers are transported by the moving conveyor to the next stage. Because the workpieces and carriers are removed from the main conveyor chain either by physical displacement or by splitting workpieces off onto divide sections, the slower tasks to be performed do not become the limiting factor in the through-put of the system.
In some situations, a series of carriers may accumulate at a work station where a task is being performed. As an oncoming carrier arrives, it will engage a stationery or slower-moving queued carrier ahead of it on the conveying line. To address this situation, a buffer stop may be employed upstream of the work station to relieve the back pressure caused by the oncoming carriers. A queue stop may also be employed to protect the carrier at the work station from being hit or struck by an oncoming carrier because collisions between carriers result in the dissipation of kinetic energy which may dislodge the workpieces disposed on the carriers as well as disrupt the task being performed at the work station.
U.S. Pat. No. 5,372,240 (hereinafter the xe2x80x9c""240 patentxe2x80x9d) shows a conveying system upon which the present invention is an improvement. When the flexible ring in that system is engaged by an oncoming carrier, the ring is simultaneously compressed in the longitudinal (or forward-rearward) direction and expands in the lateral (or side-to-side) direction. The lateral expansion of the ring of the ""240 patent causes the ring to engage the upwardly protruding sidewalls of the track section or support frame that accommodates the conveyor. The frictional engagement of the ring against the sidewalls of the track fixes the queued carrier in place; the force absorbing ability of the flexible ring, and its ability to divert shock forces outwardly toward the sidewall of the carrier support acts to brake the queued carrier as it is engaged by the oncoming carrier. Further, because the ring is flexible and resilient, the ring itself acts as a shock absorber and reduces the shock caused by the collision of the oncoming carrier with the stationary carrier and reduces the likelihood of dislodgment of workpieces from either the queued carrier or the oncoming carrier.
Depending upon the radius of the curvature in the turns of the conveyor system in the ""240 patent, the bumper configuration described therein may cause the carriers to become caught or bound by one another. However, the configuration of the present invention allows the bumper to swivel and thereby greatly reduces the chance that a carrier will become jammed in the turns of a conveyor track. The swiveling motion of the support for the bumper ring helps to align the impact forces absorbed by the ring, so that there is little eccentricity associated with the forces encountered by the bumper ring.
It is therefore an advantage of the present invention to provide a carrier for use in a non-synchronous track system that is equipped with a swiveling bumper assembly.
Another advantage of the present invention is to provide a carrier that will avoid the tendency to become jammed when rounding a curve in a track system.
Yet another advantage of the present invention is to provide a carrier in which forces imparted to the rear support of a non-moving carrier are delivered generally along a longitudinal axis of such support.